XANES and EXAFS analysis of nano-size manganese dioxide as a cathode material for lithium-ion batteries

Nano-size particles of manganese dioxide were synthesized by the reduction of the NaMnO4 precursor using fumaric acid as the reducing agent. A high specific capacity of 350 mAh g(-1) was observed during the first charge and discharge. Transmission electron microscopy examination and Mn K-edge extended X-ray absorption fine structure spectroscopy confirmed the short-range order nature of the nano-size manganese dioxide. Mn L-edge and O K-edge XANES spectra results at various potentials indicated that the oxidation reduction reaction takes place not only in the manganese 3d orbitals but also in the oxygen 2p orbitals during the charge and discharge processes and that nano-size MnO2 shows good reversibility in terms of oxidation state and local structure.